这是一个图片轮播器，请问在HTML代码中的index=1是什么意思？见代码155--159行<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>焦点轮播图</title>
<style type="text/css">
*{ margin: 0; padding: 0; text-decoration: none;}
body { padding: 20px;}
#container { width: 600px; height: 400px; border: 3px solid #333; overflow: hidden; position: relative;}
#list { width: 4200px; height: 400px; position: absolute; z-index: 1;}
#list img { float: left;}
#buttons { position: absolute; height: 10px; width: 100px; z-index: 2; bottom: 20px; left: 250px;}
#buttons span { cursor: pointer; float: left; border: 1px solid #fff; width: 10px; height: 10px; border-radius: 50%; background: #333; margin-right: 5px;}
#buttons .on { background: orangered;}
.arrow { cursor: pointer; display: none; line-height: 39px; text-align: center; font-size: 36px; font-weight: bold; width: 40px; height: 40px; position: absolute; z-index: 2; top: 180px; background-color: RGBA(0,0,0,.3); color: #fff;}
.arrow:hover { background-color: RGBA(0,0,0,.7);}
#container:hover .arrow { display: block;}
#prev { left: 20px;}
#next { right: 20px;}
</style>
<script type="text/javascript">
window.onload = function () {
var container = document.getElementById('container');
var list = document.getElementById('list');
var buttons = document.getElementById('buttons').getElementsByTagName('span');
var prev = document.getElementById('prev');
var next = document.getElementById('next');
var index = 1;
var len = 5;
var animated = false;
var interval = 3000;
var timer;
function animate (offset) {
if (offset == 0) {
return;
}
animated = true;
var time = 300;
var inteval = 10;
var speed = offset/(time/inteval);
var left = parseInt(list.style.left) + offset;
var go = function (){
if ( (speed > 0 && parseInt(list.style.left) < left) || (speed < 0 && parseInt(list.style.left) > left)) {
list.style.left = parseInt(list.style.left) + speed + 'px';
setTimeout(go, inteval);
}
else {
list.style.left = left + 'px';
if(left>-200){
list.style.left = -600 * len + 'px';
}
if(left<(-600 * len)) {
list.style.left = '-600px';
}
animated = false;
}
}
go();
}
function showButton() {
for (var i = 0; i < buttons.length ; i++) {
if( buttons[i].className == 'on'){
buttons[i].className = '';
break;
}
}
buttons[index - 1].className = 'on';
}
function play() {
timer = setTimeout(function () {
next.onclick();
play();
}, interval);
}
function stop() {
clearTimeout(timer);
}
next.onclick = function () {
if (animated) {
return;
}
if (index == 5) {
index = 1;
}
else {
index += 1;
}
animate(-600);
showButton();
}
prev.onclick = function () {
if (animated) {
return;
}
if (index == 1) {
index = 5;
}
else {
index -= 1;
}
animate(600);
showButton();
}
for (var i = 0; i < buttons.length; i++) {
buttons[i].onclick = function () {
if (animated) {
return;
}
if(this.className == 'on') {
return;
}
var myIndex = parseInt(this.getAttribute('index'));
var offset = -600 * (myIndex - index);
animate(offset);
index = myIndex;
showButton();
}
}
container.onmouseover = stop;
container.onmouseout = play;
play();
}
</script>
</head>
<body>
<div id="container">
<div id="list" style="left: -600px;">
<img src="img/5.jpg" alt="1"/>
<img src="img/1.jpg" alt="1"/>
<img src="img/2.jpg" alt="2"/>
<img src="img/3.jpg" alt="3"/>
<img src="img/4.jpg" alt="4"/>
<img src="img/5.jpg" alt="5"/>
<img src="img/1.jpg" alt="5"/>
</div>
<div id="buttons">
<span index="1" class="on"></span>
<span index="2"></span>
<span index="3"></span>
<span index="4"></span>
<span index="5"></span>
</div>
<a href="javascript:;" id="prev" class="arrow"><</a>
<a href="javascript:;" id="next" class="arrow">></a>
</div>
</body>
</html>
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